Expression of cellular prion protein ( PrPc ) in the cat central nervous system . Some findings

The expression of cellular prion protein in the central nervous system of normal cats and in cases of kainic acid injections into the mediodorsal thalamic nucleus were studied. Cellular prion protein immunodetection varied in a rostrocaudal direction: the protein was less abundant in the brainstem than in the prosencephalon. Especially abundant were the positive cells in the cerebral cortex. The immunodetection was present in areas projecting to the intermediate band of the thalamic mediodorsal nucleus and to the anteroventral nucleus of the thalamus. Some of these cells were situated around vessels in the basal prosencephalon. The immunodetection was less abundant in cases of kainic acid lesions. NAPPH-diaphorase activity was also studied. In control cases, we observed positive NADPHdiaphorase cells around vessels, especially in the basal prosencephalon. The amounts of such cells and the intensity of the reaction was lower after kainic acid lesions. Our findings lead us to propose a retrograde propagation of altered prion proteins in human spongiform encephalopathies such as fatal familial insomnia; a possible alteration of nitrergic systems is possible. Moreover, there is possibly an alteration of the prion and nitrergic physiology simply due to the destruction of the thalamic mediodorsal nucleus in fatal familial insomnia.